1. Field of the Invention
The present invention relates to protective flux coatings and to a process for applying and utilizing such coatings. More particularly, the present invention relates to a process for applying protective flux coatings to cleaned metal surfaces for delaying joining and soldering operations and to the protective flux chemical solution incorporated therein.
2. Description of Relevant Art
The relevant art is described hereinbelow.
U.S. Pat. No. 3,960,614 issued in 1976 to Stayner, entitled "WAX-FLUX COMPOSITION CONTAINING A DIESTER OF SULFOMALEIC ACID FOR SOLDERING", discloses a wax-flux composition which is used in low-temperature soldering processes related to electronic components installed on a circuit board. The wax-flux composition is applied, while in molten form, to the metal pattern side of a circuit board fitted with electronic components. When hardened at room temperature, the wax-flux allows for the trimming and soldering of the component leads to the printed circuit board with a low-melting-point alloy solder.
U.S. Pat. No. 4,028,143 issued in 1977 to Stayner, et al., entitled "WAX-FLUX COMPOSITION CONTAINING A SUCCINIMIDE SALT OF AN ALKYLARYL SULFONIC ACID FOR SOLDERING", discloses a wax-flux composition for use in low-temperature soldering processes related to electronic components which is identical to the invention disclosed in Stayner, U.S. Pat. No. 3,960,614, discussed above, except for the utilization here of a wax-soluble succinimido salt of an alkylaryl sulfonic acid. The invention contains the salt to eliminate the staining of phenolic printed circuit boards caused by the slight amount of free sulfuric acid yielded by the preparation of sulfonic acid by oleum sulfonation.
U.S. Pat. No. 4,055,725 issued in 1977 to Boynton, entitled "CIRCUIT BOARD ASSEMBLY", discloses a material, which coats the electrically conductive metal laminated side of a circuit board for holding the components in place during the soldering process. The holding material, which is applied in a liquid state and hardens to form a solid, solder-compatible, non-metallic cement having a melting point below that of solder, is disclosed as a naturally occurring or synthetic wax which may have intermixed therewith flux active agents and/or wetting agents. The holding cement is melted and displaced simultaneously with soldering. The circuit board, once coated with the cement, may be placed in storage for future soldering.
U.S. Pat. No. 4,127,692 issued in 1978 to Boynton, entitled "JIG FOR MASS SOLDERING SYSTEM", discloses a process for preparing circuit boards utilizing, in part, a coating which acts as a jig to steady or stabilize the electronic components. The coating, which is either a naturally occurring or synthetic wax, may or may not include a compatible flux,. active agent. The board is coated with the wax or wax-flux combination and then the electrical and electronic components are loaded in position on the board with their leads extending through holes thereby embedding them into or through the coating. The coating, which holds the components, secures the components in such a way so that the component leads may then be trimmed to finish length and soldered in place. The invention further discloses that the board may be placed in storage for future soldering operations.
The wax-flux and wax-flux compositions of the known art disclose coatings for use in assembling electronic components which are solid at room temperature. However, such coatings are relatively thick and are not readily usable on metallic objects which are to be joined at close tolerances. Additionally, wax-flux and wax-flux compositions are, by their nature, untidy and may remain on a person's hand or clothing after contact. Because of the negative characteristics of wax-flux and wax-flux compositions, the present invention does not employ waxes or wax-like compounds, but is rather provided in alternate forms.
In addition to the wax-flux and related wax-flux compositions, there are known a variety of soldering fluxes and means of application. This variety includes paste, liquid, powder, and gaseous fluxes and integral solder/flux forms. Paste, liquid and gaseous fluxes are applied directly, while the powder form may be applied directly or applied after mixing with a fluid and forming a paste therefrom. Integral solder/flux, which comprises a solder material having an inner core of flux, is applied directly in a one-step operation at the time of joining. While the flux forms and methods of application of these fluxes differ, they share the common disadvantages of being generally untidy and non-durable. Because of these negative characteristics, these fluxed objects must be joined and soldered immediately, or almost immediately, thereby severely limiting the amount of time allowed to pass between preparation and joining.
The present invention effectively overcomes the problems and disadvantages attendant to conventional techniques.